U.S. Episode # 35.5:

Electric Soldier Porygon

This is the famous seizure episode.  A whole bunch of kids got seizures while watching this particular episode and were sent to the hospital.  Still not shown in the United States.

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Ash and co., while investigating a clog in the Pokèmon transfer system, discover a mansion in which lives a scientist who convinces Ash to go into the program to find the problem.

Once inside, Ash discovers Team Rocket (surprise) has clogged the system, to steal Pokemon. Ash tries to stop them.  Their two Porygon's fight.  

A weird X-Wing type Anti-Virus Space ship then starts attacking Team Rocket & Ash.  Ash rescues Team Rocket just as they are about to be vaporized, but then the ship starts hunting down Ash & Gang riding on their Porygon.

The ship fires missiles at Ash.  Impending Doom is near!  Suddenly, Pikachu Jumps up and thundershocks the incoming missiles.  This scene contains about 5 seconds of alternating flashing blue & red screens that send over 1000 kids to the hospital in Japan.  Porygon escapes the transfer system just as the whole mansion blows up, and saves the day.

Pojo Note:  I don't see any reason this won't be edited by Warner Brothers some day for release in the U.S., unless the Japanese simply don't want the show to be run again.

Ash & Gang meet Porygon
Ash & Gang are "beamed" into the Pokemon Transfer system
Porygon & Team Rocket's Porygon duke it out
Ash & Pikachu try to unclog the system
Anti-Virus ship hunts down Team Rocket
Bulbasaur saves Team Rocket with Vine Whip, then goes after Ash!
Pikachu Thundershcocks the incoming missiles!
Screen alternately flashes red & blue like this for like 5 seconds.  This pattern induces illness in the brain.  Over 1000 kids in Japan Hospitalized. The whole place is about to blow up!
Porygon Gets everyone out safely just as the whole thing blows up, and gets a hug from Misty.

 

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